It is the overall goal of this project to develop sensitive immunological assays for use in clinical viral diagnosis. Phase I activities will be devoted to development of a microwell assay system based on an assay principle known as ligand replacement (a type of heterogeneous, competitive assay) and utilizing enzyme-cycling detection systems to achieve the sensitivity required. As a model system, we will use gengue-2 virus and monoclonal antibodies against this strain. Major emphasis will be placed on the evaluation of several cycling systems, on the production of conjugates of virus antigen with enzymes or coenzymes appropriate to the cycling systems, and on evaluating the efficacy of the ligand replacement assay for use in viral diagnosis. Successful completion of Phase I activities will lead in Phase II to experiments to incorporate all reagents into a dry film format suitable for use in small clinics and physicians' offices. Completion of Phase II will make available highly sensitive virus detection systems which can be used both in well equipped clinical laboratories as well as small clinics and other "field" situations.